Customized bibtex a little further...

collab.bib

@@ -32,7 +32,7 @@
     title={Efficient Volume Reconstruction for Parallel-Beam Computed
         Laminography by Filtered Backprojection on Multi-Core Clusters},
     year={2013},
-    month={Dec},
+    month={12},
     volume={22},
     number={12},
     pages={5348-5361},
@@ -67,7 +67,7 @@
     journal={PLoS ONE},
     title={Cockroaches probably cleaned up after dinosaurs},
     year={2013},
-    month={Dec},
+    month={12},
     volume={8},
     number={12},
     pages={5348-5361},
@@ -126,7 +126,7 @@
     title={Data Intensive Computing of X-Ray Computed Tomography Reconstruction
         at the LSDF},
     year={2013},
-    month={Feb},
+    month={2},
     pages={86-93},
     doi={10.1109/PDP.2013.21},
     ISSN={1066-6192},
@@ -787,7 +787,7 @@
   author = {Vogelgesang, M. and Chilingaryan, S. and Kopmann, A.},
   title = {Flexible X-Ray Image Processing on {GPUs}},
   howpublished = {Nvidia booth at Supercomputing 2011, Seattle, WA},
-  month = {},
+  month = {11},
   year = {2011}
 }
 
@@ -796,7 +796,7 @@
   title = {A GPU-accelerated Framework for Real-Time Tomographic Reconstruction},
   howpublished = {Programming and Tuning Massively Parallel Systems Summer School
       (PUMPS), Summer School, Barcelona},
-  month = {},
+  month = {7},
   year = {2011}
 }
 

refs.bib

@@ -231,18 +231,18 @@ ISSN={0003-6951},}
   year = {1988}
 }
 
-@ARTICLE{danielsson1997,
+@techreport{danielsson1997,
   title={Iterative techniques for projection and backprojection},
-  author={ Danielsson, P.E.},
+  author={Danielsson, P.E.},
   year={1997},
-  publisher={Technical report, Department of Electrical Engineering Linkopig University}
+  institution={Department of Electrical Engineering, Linkoping University}
 }
 
-@ARTICLE{mueller1998,
+@phdthesis{mueller1998,
     author = {Klaus Mueller},
     title = {Fast And Accurate Three-Dimensional Reconstruction From Cone-Beam Projection Data Using Algebraic Methods},
     year = {1998},
-    publisher = {PhD thesis, The Ohio State University}
+    school = {The Ohio State University}
 }
 
 @article{mueller1999,